Method and apparatus for cooling and dehumidifying air

ABSTRACT

A method and an apparatus for rapidly cooling and dehumidifying air within a space. In this method, air to be cooled and dehumidified is forced into a cooling zone including an evaporator ( 101 ) having fins ( 103 ) forming air channels. The fins and the air channels are preferably substantially vertical. Air is circulated above method and apparatus for carrying out the same between the space and the cooling zone in such a manner is that the evaporator can be completely cleaned and sanitized in a few minutes. Since the apparatus allows rapid shedding of any condensation off of the evaporator, freeze-ups never occur. Defrosting is thus eliminated, saving precious time and electrical energy. The above apparatus is particularly adapted for rapidly cooling food.

FIELD OF THE INVENTION

The present invention relates to a method for rapidly cooling anddehumidifying air. It also relates to an apparatus for carrying out saidmethod.

BACKGROUND OF THE INVENTION

The hospitality industry comprises over 300,000 hotels and 8 millionsrestaurants worldwide. It employs 60 millions people and contributes to950 billions US$ of the global economy. One of the major challenges itnow faces is a growing concern for health and well-being. Indeed, agrowing number of consumers want to be given assurances about thequality of the food chain.

This concern is really not surprising, considering the high rate offood-poisoning incidents occurring each year (33 millions in the U.S.A.,including 9,000 deaths).

Governments have thus stepped in and the food transformation industrynow finds itself with far more severe regulations for the safepreparation, handling, cooking, conservation and distribution of food.For example, in the United States, meat factories now have to conform tosevere standards imposed by HACCP (Hazard Analysis Critical ControlPoints). The HACCP's regulations require that food operators set-up amulti-step system designed to ensure food safety. Rapidly cooling foodimmediately after the cooling process is one of these essential steps inassuring proper food quality.

The need for such rapid cooling systems results from the fact that allfood contains micro-organisms that are potentially dangerous; Most ofthem are destroyed by the cooking process. But those that survive (2% to5%) can quickly regain their strength and begin to proliferate if givenfavorable conditions, such as in the critical temperature zone situatedbetween 15° C. and 45° C. Some can even reproduce at the frantic speedof once every 12 minutes this means that one surviving bacterium willbecome one thousand bacteria after two hours, and one billion afterseven hours!

It is often recommended that two hours be the maximum allowable coolingtime. This way, food stays within the critical zone for only a shortperiod of time. Under such conditions, risks of food poisoning aregreatly reduced. The challenge is precisely to cool down largequantities of food in less than two hours.

The market has responded to the challenge with several types ofrapid-cooling processes, one of them being called “quick chilling”,sometimes called “blast chilling”, in which food is cooled by ahigh-velocity flow of very cold air. The air temperature within thecooling zone can go as low as −15° C. Standard-sized pans (20″×12″)having depths of 1″, 2.5″ or 4″ are used to contain the food. Theprocess, better adapted to smaller operations, is widely used.

Existing blast chillers have in common two major flaws. First, theysimply cannot be properly cleaned. Cooling fans, fan motors, evaporatorfins, etc., are practically impossible to clean and sanitize. After ashort operating period, micro-organisms start proliferating on thevarious surfaces and are circulated onto the food itself by the airflow. The second major design defect is that evaporators will catch mostof the humidity given off by the food, condense it in the form ofdroplets, and freeze it as soon as the evaporator's surface temperaturefalls below 0° C. Once the water freezes up, the air flow is partiallyblocked, which lengthens the food-cooling process. The end result isthat quick chillers often have to be defrosted after each cooling cycle.Most user's manuals recommend at least one defrost cycle per day. Insome apparatus, the defrosting is done simply by leaving the door of thecooled space open while fans are running. This takes precious time. Inmost cases, an electrical resistance element is used for defrosting.This takes time and uses a lot of electrical energy.

Standard blast chillers also are quite noisy. Not surprising,considering the fact that an 80 kg unit usually has several large axialfans to move the air around.

Since fan motors are located within the cooled space, the heat energygiven off by the motors, due to internal inefficiencies, heats up theair which then has to be cooled down by the evaporator.

The cooling of food and the dehumidification of air are very closelyrelated. Indeed, in order to lower the food temperature, the air withinthe closed space where the food is placed must be dehumidified becauseof the heat and mass transfer process occurring between the food and theclosed-space air. During this process, the air becomes more and morehumid and reaches a saturation level. Once this saturation level isreached, the air will not absorb anymore heat from the food until itlooses some of its water vapor content. With that in mind, one canassume correctly that some of the previously mentioned drawbacks whichcharacterize conventional food-cooling apparatus will also be found inother dehumidifying systems such as air-conditioners, dehumidifiers,freezers, cold rooms, etc.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a method forcooling and dehumidifying air capable of overcoming the above mentioneddrawbacks.

The method for cooling and dehumidifying air within a space comprisesthe following steps:

-   -   forcing the air to be cooled and dehumidified into a cooling        zone, the cooling zone including an evaporator, the evaporator        having a plurality of fins forming air channels;    -   circulating air within the cooling zone in such a manner that        the air circulates within the air channels, the air being cooled        and dehumidified by the evaporator, humidity within the air        being condensed on the evaporator; and    -   evacuating, from the cooling zone, the droplets of condensed        water resulting from condensation.

Another object of the invention is to provide an apparatus for carryingout the method: The apparatus for cooling and dehumidifying air within aspace comprises a housing and at least one cooling zone located in thehousing. The at least one cooling zone has at least one inlet incommunication with the space. The at least one cooling zone also has atleast one outlet in communication with the space. The at least onecooling zone includes at least one evaporator located between the atleast one inlet and outlet of the at least one cooling zone. The atleast one evaporator has a plurality of fins forming air channels. Theapparatus also comprises at least one fan for circulating air betweenthe space and the at least one cooling zone, in such a manner that theair circulates within the air channels. The apparatus also comprisesmeans located in the at least one cooling zone for evacuating dropletsof condensed water resulting from condensation.

Another object of the invention is to provide an apparatus for coolingfood. The apparatus comprises an insulated housing and at least one foodzone located within the insulated housing for receiving food to becooled. The at least one food zone has at least one inlet and at leastone outlet. The apparatus also comprises at least one cooling zonelocated in the insulated housing. The at least one cooling zone has atleast one inlet in communication with the at least one outlet of the atleast one food zone. The at least one cooling zone also has at least oneoutlet in communication with the at least one inlet of the at least onefood zone. The at least one cooling zone includes at least oneevaporator located between the at least one inlet and outlet of the atleast one cooling zone. The at least one evaporator has a plurality offins forming air channels. The apparatus also comprises at least one fanfor circulating air between the at least one food zone and the at leastone cooling zone. The apparatus also comprises means located in the atleast one cooling zone for evacuating droplets of condensed waterresulting from condensation.

One of the main advantages of the above apparatus for carrying out thesame is that the evaporator can be completely cleaned and sanitized in afew minutes. Such substantially reduces the risk of contaminationnormally present in conventional quick chillers. The result is a longerperiod of safe food storage.

Moreover, since the previous apparatus allows rapid shedding of anycondensation off of the evaporator, freeze-ups never occur. The icingand defrosting processes are thus eliminated, which saves precious timeand electrical energy.

In addition, the absence of ice improves the heat transfer processbetween the air and the refrigerant, so that a smaller compressor can beused.

The objects, advantages and other features of the present invention willbecome more apparent upon reading of the following non-restrictivedescription of a preferred embodiment thereof, given for the purpose ofexemplification only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a cooling apparatus for food according to thepreferred embodiment of the invention, showing the insulated housing.

FIG. 2 is a side view of the apparatus shown in FIG. 1.

FIG. 3 is a exploded perspective view of the apparatus shown in FIG. 1.

FIG. 4 is a perspective view of the apparatus shown in FIG. 1, whichshows features within the apparatus.

FIG. 5 is a front view of the cooling zones diametrically opposed toeach others.

FIG. 6 is a perspective view of the cooling zones diametrically opposedto each others.

FIG. 7 is a top view of one of the cooling zones, showing the fins andthe air channels.

FIG. 8 is a front view of one the cooling zones shown in FIG. 7.

FIG. 9 is a side view of one of the cooling zones shown in FIGS. 7 and8.

FIG. 10 is a front, cross-sectional view of one side of the aboveapparatus showing the air flow within the cooling zone and the foodzone.

FIG. 11 is a front, cross-sectional view of the same apparatus showingthe opposite cooling zones and food zone.

FIG. 12 is a top plan view of the insulated ceiling.

FIG. 13 is a front elevational view of the insulated ceiling.

FIG. 14 is a cross-sectional view taken along lines B-B of the insulatedceiling shown in FIG. 12.

FIG. 15 is a cross-sectional view taken along lines A-A of the insulatedceiling shown in FIG. 13.

FIG. 16 is a top perspective view of the insulated ceiling shown inFIGS. 12 to 15.

FIG. 17 is a top plan view of the plate incorporating the fan inlet.

FIG. 18 is a perspective view of the vertical plate separating thecooling zone from the food zone.

FIG. 19 is a perspective view of a variant of the vertical plate shownin FIG. 18, which contains a plurality of openings.

FIG. 20 is a side elevational view of the plate incorporating the faninlet shown in FIG. 17.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIGS. 1 and 2 are front and side elevational views of an apparatus 1according to a preferred embodiment of the invention, which comprises aninsulated housing 3, in which food may be stored. FIG. 3 is an explodedview of the apparatus 1. Most of the components of said apparatus arepreferably made of stainless steel, but plastic and aluminum could alsobe used.

As illustrated in FIGS. 4, 5 and 6, the apparatus according to thepreferred embodiment of the invention has two cooling zones 102, 104each comprising one evaporator 101. Except where mentioned otherwise,both sides of the unit are symmetrical. Evaporator size may beapproximately 74 cm wide, 56 cm high and 8 cm thick. Its fins 103 may be5 cm deep and are distant from one another by about 2.2 cm.

FIGS. 7 to 9 are showing evaporators 101 design featuring a large platehaving long, deep, thick and smooth fins 103, with enough distancebetween them to create air channels 111 and permit the circulation oflarge volume of air flow. Such a large distance between fins 103 alsoprovides easy cleaning. The air flow travels along the evaporator 101,in between and along the fins 103. In standard evaporators, the airnormally flows perpendicular to a bank of finned tube. While circulatingwithin the air channels 111, the air looses its humidity and heatcontents.

Plates having fins are common in computers and the like, but in suchcases, it is used for heat dissipation, not for heat absorption. Thedissipation occurs through natural convection or via a forced,perpendicular air flow generated by an axial fan close to the plate.Moreover, in such cases, the fins do not serve as air channels.

In standard evaporators, the air normally flows perpendicularly to afinned tube, the fins themselves being very thin, fragile and very closeto one another. Humidity contained in the air condenses on the tubeitself. The water droplets resulting from condensation freeze betweenthe fins. This freezing process takes up precious cooling energy, whichreduces system efficiency. The accumulated ice also reduces theavailable fin-to-air heat transfer surface, which further reduces systemefficiency. The water freezing process continues until the passagewaybetween fins is completely blocked. The refrigeration system then has tobe shut down and a defrosting process has to be initiated, which takesup precious time and requires electrical energy.

In FIG. 10, together with a vertical plate 115, said fins 103 form alarge number of air channels 111 for the air to circulate and be cooled.Each of said fins 103 has a base and a tip and said fins 103 are thickerat the base than at the tip, providing good heat-transfer efficiency.Because of their size, shape and smooth surface, fins 103 are easy tohand clean and sanitize, either with a rag, a special brush or even witha hot water hose. This prevents bacterial growth. Preferably, thedistance between the fins is large enough to prevent droplets fromtouching at the same time to both sides of the channel formed by thefins, which would tend to improve adherence to surfaces and subsequentfreezing of the condensed water droplets. A distance between fins of,say 6 mm or more, is recommended. Larger distances, say 15 mm and up,may also be provided for easier cleaning.

The evaporator can also provide some energy storage. Indeed, after aninitial pre cooling of the system, there is a <<hold>> period duringwhich the evaporator is kept at about 0° C. During this period, the massof the evaporator helps reducing the number of On-Off cycles of therefrigeration system, improving its durability.

FIG. 10 shows the path of air flow in and out of a food zone 201, on theleft-hand side of the unit. When cooled air leaves evaporator 101 andarrives at the bottom of channel 123, droplets of condensed water areseparated from the air flow by making said air flow turn 90° and passthrough an outlet 121 of the cooling zone 102 punched in the lower partof said plate 115. The heavy droplets, being unable to follow the samepath because of the gravitational force, end up in a transversal cavity125 and into a drain hole 141. Then, water is eventually drained outsideof the apparatus 1 through an opening 143. A recipient for collectingwater could also be used instead of a drain.

After passing through the outlet 121 of the cooling zone 102, the colddry air is forced to turn upwards through another 90° because of thepresence of vertical plate 207. Said plates 115, 207 form a plenum 209inside which said air can go up and be distributed into the food zone201 via a plurality of openings 205. Inside said food zone 201, theresulting horizontal jets 203 of cold dry air are mixed (because of thewell-known entrainment effect) with the warmer, humid air above the pans501. The colder air flow circulating around the pans of hot food thuspicks up heat energy and humidity. The result is a gradual cooling ofthe food through convection.

Each side of the unit has its own evaporator 101 and plenum chamber 209,and both sides have symmetrical air flow paths, except that theleft-hand side openings 205 are offset with respect to the openings 205of the same plate at the other side. Said offsets are chosen in such away that the jets 203 directions alternate: for example, below thebottom pan 501, there is a left-hand-side jet 203 direction, while abovesaid bottom pan 501, there is a horizontal, right-hand-side jet 203direction.

The heated air is eventually pulled out from the food zone 201 by anoutlet 211 of the food zone 201 by fan 401, pushed inside plenum 129 andthen through a horizontal passageway 127 located above the food zone201. Then, said air turns 90° and goes through a short, verticalpassageway formed by plates 115 and 117, before arriving at theevaporator 101 and down between vertical fins 103 and plate 115, where anew cooling cycle begins.

The fan 401 is preferably of the radial or mixed flow type. Both typesof fans can be efficient and very silent. Both also produce a greaterpressure rise than the usual axial fans, which results in a higher speedflow of air along the fins 103. This also helps in providing a uniformair distribution inside the apparatus 1. One large radial fan rotatingat a relatively low speed (may be 1125 RPM) is normally preferable:noise will be reduced and energy saved.

In FIG. 7 to 10, the finned evaporators 101 are preferably made of castaluminum. They are cooled by an internal refrigerant circuit, consistingof a coil 113 embedded in the evaporators 101 during the castingoperation. Said evaporators 101 are part of a common vapor-compressionrefrigeration system.

Now referring to FIG. 11, while fan 401 is located inside a cold,insulated zone, its motor 405 is located outside of said cooling zones102, 104 above the insulated ceiling 301, its driving shaft 403 goingthrough a hole in the ceiling 301. The ceiling is fabricated out of twovacuum/heat formed plastic plates, separated by about 6 cm of urethanefoam. Ceiling 301 and plate 303 provide the walls for plenum 129. Alsoshown in FIG. 17 to 20, said plate 303 incorporates the fan inlet ring305 and is hinged 133 to the internal back wall of the apparatus 1.

The boundaries of said cooling zones 102, 104, appearing in FIG. 11, arethe insulated ceiling 301, the insulated vertical walls 119 and theinsulated floor 145. FIGS. 12 to 16 show the, insulated ceiling 301.

FIGS. 17 to 20 show plates 115, 207, which form the left-hand-side andthe right-hand-side plenums 209, are hinged 131 to the internal backwall of the apparatus 1. This way, they can be opened and closed likeordinary doors, for cleaning purposes, or removed for repairs.

As mentioned earlier, in this apparatus 1, freeze ups cannot occur sincecondensed humidity cannot accumulate on the evaporators 101. Indeed,getting rid of the condensed water droplets can be facilitated in anumber of ways: the evaporators 101 are installed vertically; airchannels 111 between fins 103 are also vertical; air flows between fins103, vertically from top to bottom; the air velocity is high betweenfins 103 (may be 10 m/s±5); the fins 103 are smooth; the fins 103feature a hydrophobic coating such as Teflon.

Because of these characteristics, gravity helps water droplets to travelvertically down along the fins 103 and the air flow also helps waterdroplets to travel vertically down along the fins 103. The smoothing andhydrophobic coating of the fins 103 make the droplets slide down moreeasily along the fins 103.

Three plenums are built into the apparatus described above. The firstplenum 129 is located above food zone 201. Its function is to ensure auniform horizontal air distribution through the evaporator fins 103, andthus a uniform cooling of the air. The other two plenums 209 are locatedbetween vertical plates 115 and 117, on each side of the food zone 201.Their function is to ensure a uniform horizontal and verticaldistribution of cooled air in the food zone 201. This, in turn, producesa uniform cooling of the food everywhere inside the food zone 201.

Plenums always have to be as large as possible. But again, a compromisehas to be reached between plenum efficiency and global unit size.

Even though plenums are a common tool in heating and cooling systems,they are used here in a novel way, since they are installed in cascade,i.e. air goes through two plenums on its trip between the fan 401 andthe food zone 201. Moreover, this is the only unit where the air flow issplit in two before going to the evaporators. Finally, all three plenumscan easily be opened and/or dismantled for cleaning purposes, which is afirst.

It has been found experimentally that most of the water-vaporcondensation occurs during the first part of the food-cooling cycle,while the food surface temperature is approximately above 10° C.Consequently, if the evaporator 101 temperature is kept at, say, 1° C.during that period, no icing will occur on the evaporator 101 surface;the water droplets will simply slide along said fins 103 and accumulateat the bottom of the cooling zone where they will be collected by atransversal cavity 125, and will be drained 143 to the outside of theunit.

Control strategy also contributes to the elimination of defrostingcycles, which is an important time and energy-saving feature. Control ofthe evaporator 101 temperature can be obtained in a number of ways. Themost usual technique being the use of the hot-gas-bypass technique, inwhich part of the flow of hot gases from a compressor outlet are sentdirectly to the evaporator 101 without first going through a condenser.By regulating, via a hot-gas-bypass valve (or HGBV), the quantity ofgases going through the bypass, one can control the evaporator 101temperature.

It has also been found, however, that even when the evaporatortemperature is not kept under control during the cooling process, verygood results are still obtained, hardly any freezing will occur on theplate. Most of the humidity has' already condensed when the platetemperature gets below 0° C. This provides for much simpler controls.

As soon as the food surface temperature has dropped approximately below10° C. (and/or the air temperature within the food zone has dropped to4° C. approximately), the evaporator 101 surface temperature can beallowed to drop to a second set-point temperature of approximately −20°C., with no fear of evaporator-surface icing, since very little humidityis then circulated.

As the food core temperature reaches the desired final set pointtemperature, two methods can be used for ending the rapid-coolingprocess to avoid the freezing of the food. One method is to stop thecompressor and let the evaporator 101 temperature come back to the firstset-point temperature of 1° C., the fan 401 still circulating the air.The other method is to keep the compressor running, but use the HGBV tosend hot refrigerant gas into the evaporator 101 until it warm up toapproximately 3° C. Then, after closing the HGBV, the system would letthe system run and come back to the first set-point temperature of 1° C.

From then on, the control system acts as a thermostat trying to keep theair temperature at about 3° C., just like in a standard refrigerator.The core temperature will then slowly come down from 10° C. to 3° C. Ofcourse, all these set points are adjustable.

Alternative Embodiments

Although the present invention has been explained hereinabove by way ofa preferred embodiment thereof, it should be pointed out that anymodifications to this preferred embodiment within the scope of theappended claims is not deemed to alter or change the nature and scope ofthe present invention.

Several alternative embodiments of the present invention can be created.For example, a prototype unit according to the present invention hasbeen build. The unit has a nominal capacity of 40 kg of solid food (e.g.meat, vegetables, pastry, etc.) and accommodates up to 10 standard-sizepans. The unit has two evaporators. A refrigeration compressor has 1.5hp, or about 25% less hp than a refrigeration compressor in aconventional chiller.

Another apparatus for cooling food according to the present inventionhaving a 16 kg food capacity has been designed, built and tested,featuring a single vertical evaporator located vertically on aright-hand side of a food zone. The evaporator, including its fins, was40 cm long, 50 cm high and 9 cm thick. The air flow was generated by asingle centrifugal or radial fan also located vertically on theright-hand side of the food zone. In this apparatus, air to be cooled ispushed by the fan through a thin, wide passageway, through the top ofthe evaporator, and then down along the evaporator, between its verticalfins. When cooled air leaves the evaporator droplets of condensed waterare separated from the air flow by making said air flow turn 90°. Theheavy droplets; being unable to follow the same path because of thegravitational force, end up in a transversal cavity and into a drainhole. The air flow then travel horizontally to the left through apassageway and then up through a plenum, from which the air isdistributed into the food zone through openings for cooling the food.The colder air flow circulating around the pans of hot food thus picksup heat energy and humidity. The result is a gradual cooling of the foodthrough convection.

The preferred embodiment of the invention features a single radial fan.However, provided some modifications are made to the design of the unit,other types of fans could be used. Furthermore, two or more fans couldbe used. There are advantages to using a single, large fan, rotating atlow speed, instead of two or more smaller fans. Firstly, there is ansignificant cost reduction. Secondly, a single fan results in animportant noise level reduction and in energy efficiency.

The apparatus for cooling food according to the present invention has afan, which motor is located outside of the cooling zone, i.e. outside ofthe insulated housing. Several advantages are thus provided. Firstly,the cooling zone can be completely washed and sanitized using a waterhose, without fear of electrical shocks. Secondly, heat loss from themotor of the fan is not transferred to the cooling zone, thus reducingthe heat to be removed from said cooling zone.

One or more evaporators can be used within the apparatus, but inpractice, one or two evaporators are preferred. Those evaporators can beflat or curved. Even cylindrical ones are an interesting possibility.

Tests have also been successfully performed with a vertical evaporatorhaving horizontal fins, the air then circulating horizontally betweenthe fins. In such a case, the air velocity between fins had to beincreased somewhat to between 5 and 15 m/s approximately, in order forthe droplets to be dragged towards the drain.

Although long fins are preferred, shorter will do fine. Also, the finpitch (distance between fins) can be varied at will, but there willalways be a compromise to be reached between ease of cleaning and heattransfer efficiency.

Instead of being cast, the evaporator can be made from extruded aluminumprofiles. In such a case, the front of the evaporator featured the deeplongitudinal fins while its back featured a plurality of longitudinalgrooves. The grooves featured have, say a 4.5 mm radius and a circularshaped bottom. The coil, fabricated using a plurality of straight coppertubes having, say a 7.8 mm-diameter, is designed to fit into thegrooves. Proper thermal contact between the copper coil and the wall ofthe groove is first established by pouring hot liquid zinc into thegroove. Results were excellent.

A simpler and cheaper method is also possible: the diameter of thestraight copper tubes is chosen so that it closely fit into the circulargrooves. After being positioned into the grooves, the tubes are partlyflattened out using a press brake to establish a very good mechanicaland thermal contact between tubes and the aluminum extrusion.

Evaporators can be made from any suitable material, using any knownfabrication process. They can be cooled by any suitable primary orsecondary refrigerant. For example, such finned evaporators could becooled using a circulating solution of glycol. Even pure water can beused in some of the applications mentioned below.

The cooling of the food is more efficient by controlling parameters suchas the food-core temperature, the evaporator temperature and the airtemperature within the insulated housing. It should be mentioned,however, that even when controlled solely with a food-core probe and anon/off thermostat, the system will give very acceptable results. It willalso work quite well with a simple timer.

The present invention has several other applications. It will beparticularly useful in applications in which the circulated air mustboth be cooled and dehumidified, which is the case in air conditioners,air dehumidifiers, freezers, refrigerating rooms, etc.

Another application of the invention concerns air conditioners. In orderfor air conditioners to be efficient, they have to cool the air quicklyand remove humidity efficiently. To ensure safety, they should also bevery easy to clean. Otherwise, users will neglect the cleaning task andmicro-organisms will start proliferating within the air circuit,especially in between the closely-spaced fins of the evaporator, whichare most of the time filled with condensed water. These problems arevery similar to those facing the quick chiller designer. The presentinvention can provide a solution to these efficiency and safety problemsby providing an apparatus that can be cleaned in a few minutes, whileconventional air conditioners simply cannot be cleaned properly.

Moreover, since condensed-water droplets are quickly eliminated from theevaporator surface, the heat transfer between the air and the evaporatoris much improved. This permitted a slightly higher evaporatingtemperature of the refrigerant and thus a better operating coefficientof performance (COP) and a larger capacity of the system. Also, thequantity of water removed from the air in time unit is appreciablyhigher. The use of a centrifugal fan instead of the usual axial fan alsogives an important reduction in noise level of the unit.

Another application of the invention concerns air dehumidifiers. Inorder for air dehumidifiers to be efficient, they should remove as muchhumidity as possible from the air. To ensure safety, they should also bevely easy to clean. Theses are problems that can be solved by thepresent invention.

The present invention may also be used to condense water vapourgenerated, for example, by the action of the sun on salty or pollutedwater. The end product will then be potable water. After minormodifications and the addition of components for storing the condensedwater, the invention will thus become an efficient desalination plant ora water purification system. People in regions around oceans or ontropical islands would welcome such a technology.

Such a desalination plant (or water purification system) could even bemade very cheaply by eliminating the mechanical refrigeration systemaltogether, replacing it with a continuous salt water (or pollutedwater) circulation. This would work as long as the available water isabout 10° C. (or more) colder than the atmosphere. Moreover, the plateshaving a plurality of fins forming air channels could be made out offormed thin sheet metal or even out of thin thermoformed plastic sheets.One possible design for the finned plates would be assembling two of theformed sheets back to back, the cold water circulating between the twofinned sheets, preferably from bottom to top, while the flow of air onthe outside, between fins, would preferably be vertically downward. Theflow of air would be generated by a fan of any available type.

In all the preferred and alternative embodiments, it could beinteresting to monitor operational parameters such as the evaporatortemperature, the air temperature once it leaves the evaporator, thecooled-space air temperature. However, tests have shown that notmonitoring these parameters did not have an important effect on theefficiency of the apparatus. Monitoring the various parameters ishowever recommended for security reasons or to improve the durability ofthe components of the apparatus.

Of course, in the case of the blast chiller, the food-core temperaturebecomes an important parameter that can be monitored in order toindicate to the refrigeration system when to stop the rapid-coolingprocess. The evaporation and condensation pressures also are importantparameters that one might like to monitor, in order to avoid operatingconditions that would decrease the life of the costly compressor.

In the above mentioned simplified desalination plant, there would be noreal need for monitoring any of the operating parameters, except maybethe salt water flow.

1. A method for cooling and dehumidifying air within a space, comprisingthe steps of: forcing said air to be dehumidified into a cooling zone,said cooling zone including an evaporator plate having a plurality offins forming air channels; continuously evacuating from said coolingzone droplets of condensed water resulting from condensation; andcirculating air within said cooling zone in such a manner that said aircirculates within said air channels, said air being cooled anddehumidified by said evaporator plate, the humidity within said airbeing condensed on said evaporator plate.
 2. A method according to claim1, further comprising the following step: preventing formation of a coldwater layer on the surface of said evaporator plate by rapidly removingsaid droplets of condensed water from said surface of said evaporatorplate.
 3. A method according to claim 1, wherein said droplets ofcondensed water are rapidly removed from said evaporator plate bycirculating said air along said air channels, and are evacuated fromsaid cooling zone before freezing.
 4. A method according to claim 1,wherein said air channels are being substantially vertical in such amanner that said air circulates substantially vertically downward.
 5. Amethod according to claim 1 wherein said fins are covered by ahydrophobic coating.
 6. An apparatus for cooling and dehumidifying airwithin a space, comprising: a housing; at least one cooling zone locatedwithin said housing, said at least one cooling zone having at least oneinlet in communication with said space, said at least one cooling zonealso having at least one outlet in communication with said space; atleast one fan for circulating air between said space and said at leastone cooling zone; and means located within said at least one coolingzone for continuously evacuating droplets of condensed water resultingfrom condensation, said at least one cooling zone including at least oneevaporator plate located between said at least one inlet and outlet ofsaid at least one cooling zone, said at least one evaporator platehaving a plurality of fins forming air channels within which said aircirculates.
 7. An apparatus according to claim 6, wherein said airchannels are being substantially vertical in such a manner that said aircirculates substantially vertically downward.
 8. An apparatus accordingto claim 6, wherein said fins are covered by a hydrophobic coating. 9.An apparatus according to claim 6, wherein said fan is devised tocirculate air with enough velocity to remove said droplets of condensedwater from said at least one evaporator plate.
 10. An apparatusaccording to claim 6, wherein said at least one evaporator platecomprises an internal refrigerant circuit embedded therein.
 11. Anapparatus according to claim 6, wherein each of said fins has a base anda tip and said fins are thicker at the base than at the tip.
 12. Anapparatus according to any one of claims claim 6 toll, wherein saidmeans for evacuating droplets of condensed water comprises a drain. 13.An apparatus according to claim 6, wherein said means for evacuatingdroplets of condensed water comprises a recipient for collecting water.14. A cooling apparatus for food comprising: an insulated housing; atleast one food zone located in said insulated housing for receiving foodto be cooled, said at least one food zone having at least one inlet andat least one outlet; at least one cooling zone located within saidinsulated housing, said at least one cooling zone having at least oneinlet in communication with said at least one outlet of said at leastone food zone, said at least one cooling zone also having at least oneoutlet in communication with said at least one inlet of said at leastone food zone; at least one fan for circulating air between said atleast one food zone and said at least one cooling zone; and meanslocated within said at least one cooling zone for continuouslyevacuating droplets of condensed water resulting from condensation, saidat least one cooling zone including at least one evaporator platelocated between said at least one inlet and outlet of said at least onecooling zone, said at least one evaporator plate having a plurality offins forming air channels within which said air circulates.
 15. Acooling apparatus according to claim 14, wherein said air channels arebeing substantially vertical in such a manner that said air circulatessubstantially vertically downward.
 16. A cooling apparatus according toclaim 14, wherein said fins are covered by a hydrophobic coating.
 17. Acooling apparatus according to claim 14, wherein said fan is devised tocirculate air with enough velocity to remove said droplets of condensedwater from said at least one evaporator plate.
 18. A cooling apparatusaccording to claim 14, wherein said at least one evaporator platecomprises an internal refrigerant circuit embedded therein.
 19. Acooling apparatus according to claim 14, wherein each of said fins has abase and a tip and said fins are thicker at the base than at the tip.20. A cooling apparatus according to claim 14, wherein said means forevacuating droplets of condensed water comprises a drain.
 21. A coolingapparatus according to claim 14, wherein said means for evacuatingdroplets of condensed water comprises a recipient for collecting water.22. A cooling apparatus according to claim 14, wherein the housingcomprises two sides opposite to each other, each of said sides havingone of said at least one food zone with said at least one outlet of saidone food zone located on top of it, each of said sides also comprisingone of said at least one cooling zone and at least one opening locatedat a bottom of said at least one cooling zone, said opening definingsaid inlet of said at least one food zone and said outlet of said atleast one cooling zone.
 23. A cooling apparatus according to claim 22,wherein each of said sides is provided with a plate defining a plenumlocated within said at least one food zone, said plenum being incommunication with said at least one inlet of said food zone, each ofsaid plates being provided with a plurality of openings, the openings ofeach of said plates at one end being offset with respect to the openingsof the same plate at the other end.